1. Field of the Invention
The present invention generally relates to an electronic apparatus provided with a control unit. More specifically, the present invention relates to an electronic apparatus provided with a control unit, peripheral circuits whose operations are controlled by the control unit, and a rechargeable battery to feed operation power to the control unit and the peripheral circuits, and to a control method thereof.
2. Background Information
CPU-type electronic clocks that are used in microcomputers are known in prior art. Such CPU-type electronic clocks are provided with a CPU (control unit), ROM and RAM, an oscillation circuit that generates a system clock, and peripheral circuits composed of clock driving circuits that are controlled by the CPU and of circuits that generate interrupts. There are electronic clocks of this type that are provided with a reset generation circuit that outputs an initialization signal to the CPU when a reset signal is produced. Examples of the use of the circuit include when the user carries out a reset operation, when power ON is detected (battery change), and when a reset signal is input to the reset terminal exposed when the back cover of the clock is opened (as shown in Japanese Laid-Open Patent Application No. 6-161608).
In a CPU-type electronic clock, since the peripheral circuits operate at a voltage V2, which is lower than an operation-assured voltage V1 of the CPU (control unit), the peripheral circuits will operate while the remaining capacity of the battery is between voltages V1 and V2, but the CPU may start abnormal control routines. When the CPU carries out abnormal control routines, the peripheral circuits are controlled by such control routines, and the peripheral circuits also do not operate in a normal manner.
Nevertheless, even if the user resets the system when the peripheral circuits stop operating in a normal manner, the CPU cannot carry out initialization procedures when the remaining capacity of the battery is low (in the vicinity of voltage V2, for example), and abnormal operation in the peripheral circuits cannot be stopped. For this reason, when a configuration is adopted that uses a rechargeable battery and the rechargeable battery is recharged with power generated by the power generation apparatus (solar panel, or the like), once the CPU begins an abnormal routine due to a drop in the voltage of the rechargeable battery, the rechargeable battery is suitably recharged, and so the abnormal routine continues, circuits not expected to operate suddenly begin to operate (continuous motor pulse output, for example), and power is wasted.
A condition in which such power is consumed is disadvantageous in that the rechargeable battery does not satisfactorily charge, the electronic apparatus cannot be activated, and other problems are created unless the power generating capacity of the power generating device is increased (unless a strong light is directed to the solar panel, for example).
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved an electronic apparatus provided with a control unit, peripheral circuits whose operations are controlled by the control unit, and a rechargeable battery for feeding operation power to the control unit and the peripheral circuits, and to a control method thereof. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.